Reflectometer

• US 20030214655A1
• Filed: 06/02/2003
• Published: 11/20/2003
• Est. Priority Date: 10/31/1997
• Status: Active Grant

• Current Assignee: Irwin Weitman, John Weiss
• Original Assignee: Irwin Weitman, John Weiss
• Inventors: Weiss, John, Weitman, Irwin
• Granted Patent: US 6,952,263 B2
• Time in Patent Office: Days
• US Class Current: 356/402
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/4738 Diffuse reflection precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration, e.g. also for testing fluids, fibrous materials
• CPC Class Codes: G01N 21/8483 Investigating reagent band test-element handling not specific to a test method G01N33/4875; analytical elements specific to chemical analysis of biological material G01N33/52; autometer with reagent band G01N35/04

Abstract

The present invention comprises reflectometer for detecting and measuring subtle changes in color and shade of color. In general, a pulsating light source illuminates a target surface which possesses a certain color and shade of color. An optical detection circuit synchronously detects light that is reflected from the target surface and generates an output signal whose voltage is indicative of the color and shade of the target surface. This voltage is then processed to make an evaluation and identification of any measurable quantity or quality that is represented by the detected color or shade of color.

Claims

1. A reader head for a reflectometer, comprising:

at least two light emitting diodes;

an optical detector; and

means for mounting the light emitting diodes each at an orientation offset angled away from an orientation of the optical detector so as to provide for substantially uniform illumination of a target surface with minimal specular reflection to the optical detector.

2. The reader head, according to claim 1, wherein the orientation of the optical detector is normal to the target surface.

3. The reader head, according to claim 1, wherein the offset angle is between forty and forty-five degrees.

4. The reader head, according to claim 1, wherein the target surface comprises a color developing membrane of a transdermal patch, and the reader head is adapted for mating with the color developing membrane of the transdermal patch.

5. The reader head, according to claim 1, wherein the two light emitting diodes are of different color.

6. An apparatus, comprising:

a light source for emitting light having an intensity that varies with changes in temperature;

an optical detector for detecting light from the light source and generating a first output indicative of detected light;

a temperature sensor thermo-mechanically coupled to the light source, the sensor generating a second output indicative of temperature of the light source; and

means for mathematically correcting a voltage level of the first output in accordance with the second output to account for detected changes in light source temperature.

7. The apparatus, according to claim 6, wherein the light source comprises at least one light emitting diode, and wherein the temperature sensor comprises a diode means having an operating characteristic substantially complementing that of the light emitting diode.

8. An apparatus, comprising:

a light source for emitting light having an intensity that varies with changes in temperature;

an optical detector for detecting light from the light source and generating an output indicative of detected light;

a temperature compensator thermo-mechanically coupled to the modulated light source; and

means responsive to the temperature compensator for controlling operation of the light source to counteract for any variations in light intensity due to changes in light source temperature.

9. The apparatus, according to claim 8, wherein the light source comprises at least one light emitting diode, wherein the temperature compensator comprises a diode, and wherein the means for controlling comprises a series electrical connection of the diode with the light emitting diode.

10. An apparatus, comprising:

a light source for emitting light having an intensity that varies with changes in voltage drop across the light source;

an optical detector for detecting light from the light source and generating an output indicative of detected light;

a sensor for measuring voltage drop across the light source; and

means for mathematically correcting a voltage drop to account for variations in light intensity due to changes in voltage drop.

11. A reflectometer, comprising:

a light source for emitting light to illuminate a target surface which possesses a certain color and shade of color;

an optical detector circuit for detecting light that is reflected from the target surface and generating a substantially steady DC output voltage that is indicative of the color or shade of color at the target surface;

a processor for converting the steady DC voltage indicative of the color or shade of color at the target surface into a corresponding quantity or quality measurement; and

means for controlling modulation of the light source in a first mode to illuminate the target surface and in a second mode to remotely communicate data identifying the corresponding quantity or quality measurement over optical communications link.

12. The reflectometer, according to claim 11, wherein the optical detector circuit comprises:

an optical detector for detecting light that is reflected from the target surface and generating a first output indicative of detected light;

means for processing the first output to generate a feedback signal for application to the optical detector to compensate for any DC voltage shift in the first output resulting from the detection of ambient light by the optical detector, and differentially amplify the first output to generate a second output; and

a detector for synchronously demodulating the second output to generate the substantially steady DC output voltage that is indicative of the color or shade of color at the target surface.

13. The reflectometer, according to claim 12, wherein the optical detector comprises:

a photo transistor for receiving and detecting light that is reflected from the target surface and generating a first differential signal;

a transistor for setting the quiescent operating point and generating a second differential signal; and

means for connecting the photo transistor and transistor at a common emitter connection in a differential configuration.

14. The reflectometer, according to claim 13, further comprising a current mirror for supplying fixed constant current into the common emitter connection between the differentially connected photo transistor and transistor.

15. The reflectometer, according to claim 14, wherein the means for processing processes the second differential signal to generate the feedback signal for application to the photo transistor to bias the photo transistor to the quiescent operating point.

16. The reflectometer, according to claim 15, wherein the means for processing comprises an integrator for comparing the second differential signal to a reference voltage and integrating a result of the comparison to generate the feedback signal, wherein the feedback signal is indicative of an error between the quiescent operating point and a shift caused by DC ambient light detected at the photo transistor.

17. The reflectometer, according to claim 13, wherein the light source comprises:

at least two light emitting diodes; and

means for mounting the light emitting diodes each at an orientation angle away from an orientation angel of the optical detector so as to provide for substantially uniform illumination of the target surface with minimal specular reflection to the optical detector.

18. The reflectometer, according to claim 17, wherein the two light emitting diodes are of different color.

19. The reflectometer, according to claim 18, further including means for alternately pulsing the light emitting diodes of different color.

20. The reflectometer, according to claim 12, wherein the detector for synchronously demodulating comprises a full wave synchronous detector producing a DC voltage proportional to the peak to peak voltage of the second output signal.

21. A reflectometer, comprising:

a light source for emitting light to illuminate a target surface which possesses a certain color and shade of color;

an optical detector circuit for detecting light that is reflected form the target surface and generating a substantially steady DC output voltage that is indicative of the color or shade of color at the target surface;

a stored look-up table or mathematical formula correlating steady DC voltage values to corresponding quantity or quality measurements for each one of a plurality of different tests; and

a processor for consulting the stored look-up table or mathematical formula for a certain test being performed, and converting the steady DC voltage indicative of the color or shade of color at the target surface into a corresponding quantity or quality measurement in accordance with that certain test.

22. The reflectometer, according to claim 21, wherein the light source is a modulated light source and wherein the optical detector circuit comprises:

an optical detector for detecting light that is reflected from the target surface and generating a first output indicative of detected light;

means for processing the first output to generate a feedback signal for application to the optical detector to compensate for any shift in the first output resulting from the detection of ambient light by the optical detector, and differentially amplify the first output to generate a second output; and

a detector for synchronously demodulating the second output to generate the substantially steady DC output voltage that is indicative of the color or shade of color at the target surface.

23. The reflectometer, according to claim 22, wherein the optical detector comprises:

a photo transistor for receiving and detecting light that is reflected from the target surface and generating a first differential signal;

a transistor for setting the quiescent operating point and generating a second differential signal; and

means for connecting the photo transistor and transistor at a common emitter connection in a differential configuration.

24. The reflectometer, according to claim 22, wherein the detector for synchronously demodulating comprises a full wave synchronous detector producing a DC voltage proportional to the peak to peak voltage of the second output signal.

25. The reflectometer, according to claim 21, further including means for calibrating the reflectometer to each stored look-up table or mathematical formula for each one of the plurality of different tests.

26. A reflectometer, comprising:

a light source for emitting light to illuminate a target surface which possesses a certain color and shade of color;

an optical detector circuit for detecting light that is reflected from the target surface and generating a substantially steady DC output voltage that is indicative of the color or shade of color at the target surface;

a stored look-up table or mathematical formula correlating steady DC voltage values to corresponding quantity or quality measurements;

means for calibrating the reflectometer to determine an offset for application to read DC output voltages corresponding to a certain color or shade of color; and

a processor for the determined offset to adjust the steady DC voltage indicative of the color or shade of color table or mathematical formula and converting the adjusted steady DC voltage into a corresponding quantity or quality measurement.

27. The reflectometer, according to claim 26, wherein the means for calibrating comprises means for determining an offset for application to read DC output voltages at end points each corresponding to a certain color or shade of color.

28. The reflectometer, according to claim 26, wherein the processor further interpolates the offset for application to read DC output voltages not corresponding to the certain color or shade of color.